The present invention relates to a rotary compressor which is especially suited for use in compressing a refrigerant fluid in an air conditioning system for a motor vehicle or a building.
A rotary compressor has been developed in which a lubricating oil sump is pressurized by refrigerant fluid at the compressor outlet. An oil passageway leads from the oil sump through the pump rotor to the inlet, oil being forced through the oil passageway and lubricating the internal parts of the rotor. At the inlet, the oil is entrained in the refrigerant fluid and compressed therewith, lubricating the areas of sliding contact between the rotor and a cylinder in which the rotor is operatively disposed.
The oil must be removed from the refrigerant fluid and returned to the oil sump before the refrigerant fluid is discharged from the compressor. If the oil were allowed to remain entrained in the refrigerant fluid as the same is passed through the axternal refrigerant circuit, the cooling efficiency would be drastically reduced. In addition, the amount of oil in the compressor may drop so low that the rotor would seize in the cylinder.
Two means have been heretofore proposed to remove the entrained oil from the refrigerant fluid at the outlet of the compressor. The first method is to provide a large expansion chamber between the outlet of the cylinder and the outlet of the compressor. Expansion of the refrigerant fluid in the expansion chamber causes the entrained oil to precipitate and return to the oil sump under the influence of gravity. One drawback of this method is that the necessarily large size of the expansion chamber increases the overall size of the compressor to an unacceptable extent. Another drawback is that since the fluid takes the shortest path through the expansion chamber the reduction of velocity is not sufficient for gravity to effectively separate the oil from the refrigerant fluid.
The second method is to provide a wire gauze oil separating filter in the outlet of the compressor. These filters, however, are unsatisfactory since they clog easily, thereby obstructing the fluid flow through the compressor. In addition, such filters must be replaced periodically, thereby imposing an undesirable maintenance requirement.